1. Field of the Invention
The present invention relates to instruments for indicating or recording the sizes and shapes of irregularities on a surface, and, more particularly, to hand-held and portable instruments for measuring surface irregularities.
2. Prior Art
In many manufacturing operations, it is often necessary to determine the contour or profile of the finished product. For example, in paper making operations, it is necessary to determine the amplitude and location of ridges and wavy surfaces that appear on the surface of a coiled web of paper. The data regarding the surface irregularities is useful as the paper is processed through various steps to the final product, such as coating, calendering, rewinding, and cutting.
One example of such an instrument is disclosed in U.S. Pat. No. 3,540,270. This device determines reel hardness, or the resiliency of a surface of a reel, and consists of a frame having front and rear rollers, a wheel which is rotatably mounted to a yoke extending from a spring arm mounted intermediate the rollers, and a series of protrusions extending from the periphery of the wheel. As the device is moved along the surface of a coiled web of paper, the protrusions on the wheel engage and deflect the surface of the paper and cause the wheel to deflect away from the paper thereby activating a recording device, such as an accelerometer, which generates a signal recorded on a chart recorder to give a continuous trace. This device measures the hardness of a coiled web of paper by measuring the penetration of the protrusions on the wheel into the surface of the web. The wheel is urged toward the web by a coil spring and the entire frame is held against the coil by a boom extending upwardly from a carriage mounted to travel in a direction which is parallel to the central axis of the coiled web.
This device has several disadvantages. For example, the device must be urged against the surface to be measured so that the spring holding the wheel against the surface may be properly deflected. This requires the use of a boom and a carriage which add to the cost of the device and impair its portability. In addition, the proximity of the wheel to the front rollers reduces the ability of the device to measure variations in surface profile. Since the wheel is virtually co-axial with one of the rollers, it cannot measure the differences in distances from the frame to the surface because that distance is maintained constant at the rollers.
Another disadvantage lies in the recording mechanism used for the device. The device requires sophisticated electronic equipment, such as accelerometers, which generate a signal sent to a chart recorder which generates a trace. This significantly adds to the cost and complexity of the mechanism and also reduces its portability.
Accordingly, there is a need for a surface profile recorder which is portable and preferably hand-held, inexpensive to manufacture, and has a self-contained recording apparatus that can generate a trace indicating the irregularities of the surface measured without need of sophisticated electronic apparatus.